1. Technical Field
The present invention relates to a wavelength variable interference filter and a process for producing a wavelength variable interference filter.
2. Related Art
In the past, a wavelength variable interference filter having a pair of high-reflection mirrors disposed to face each other on the facing surfaces of a pair of substrates, respectively, was known. In such a wavelength variable interference filter, light is reflected between the pair of mirrors and only light of a specific wavelength is transmitted, and light of other wavelengths is canceled by interference, thereby transmitting only light of a specific wavelength among incident light.
For example, in an electrostatic-driven wavelength variable interference filter described in JP-A-2005-165067, due to an electrostatic attractive force generated between driving electrodes provided on the facing surfaces of a pair of substrates, respectively, a support section (diaphragm) is deformed, thereby varying a gap between a pair of mirrors. A movable section of the substrate provided with a second reflection film (movable mirror) is formed such that the thickness thereof is large so as to prevent the movable mirror from bending.
In the wavelength variable interference filter described in JP-A-2005-165067, the substrate provided with the movable section and the support section is formed by etching a sheet of substrate, however, it is necessary to make the thickness of the substrate before etching large for making the thickness of the movable section large. However, when the thickness of the substrate is large, it is necessary to perform etching for a long time for forming the support section and also a variation in the thickness of the support section is increased due to a variation in etching. In this case, the pair of mirrors cannot be maintained in a parallel state when displacing the movable section, and therefore, there was a problem of a deterioration in spectroscopic accuracy such as a decrease in resolution of light dispersed by the wavelength variable filter.